Start of by making a new photoshop document, with dimensions of 200x200 and a white background. Create some large, thick, light green (DBF5AD) text, preferably with rounded corners. I used Arial Black 200 pt for this, so I had to round off the the corners (image b).

a)

b)

Step 2.

Make a selection using the text and then fill it with a darker green (2F8B48) on a new layer. Now feather (select > feather) and contract (select > modify > contract) the selection by 7 pixels, and then delete the area that's selected (image b).

a)

b)

Step 3.

Create a layer below the first 2 and then make a selection using the text again. Expand the selection by 3 pixels and then fill it with a lighter green 3. (A8CFAF).